1. Field of the Invention
The present invention relates to an exhaust pipe layout structure for vehicles in which an engine having a cylinder head disposed on an upper side thereof and a transmission coupled to the engine are transversely mounted at a front portion of a vehicle body and in which an exhaust pipe extends from an exhaust manifold coupled to a rear side of the cylinder head extends toward the rear of the vehicle body.
2. Description of the Related Art
An exhaust pipe layout structure as described above is known in Japanese Patent Unexamined Publication No. Hei. 5-1530 (JP-A-5-1530). In this conventional exhaust pipe layout structure, a power unit is transversely mounted which comprises an engine and a transmission which are made integral with the engine being disposed such that the crankshaft is oriented in a transverse direction of the vehicle body and that the axes of the cylinders are inclined rearward. In addition, an exhaust pipe having an inclined portion extending toward the rear in a downward direction and a horizontal portion extending to the rear is connected to a rear end of an exhaust manifold coupled to a rear side of a cylinder head of the engine, and a catalyzer is connected to a rear end of the exhaust pipe. The exhaust pipe is connected to the exhaust manifold and the catalyzer via flexible joints at the front and rear ends thereof, respectively. The vibration of the exhaust pipe is designed to be controlled by disposing the roll center of the power unit and the two flexible joints in a specific positional relationship.
In a front-wheel-drive vehicle in which the power unit is transversely mounted, the drive shafts for driving the left and right front wheels extend in transverse directions of the vehicle body from a rear portion of the transmission, and the steering gear box for steering the front wheels is disposed behind the drive shafts in such a manner as to be oriented in a transverse direction of the vehicle body. In this construction, when the exhaust pipe extending from the exhaust manifold coupled to the rear side of the cylinder head is tried to be led downwardly below the floor panel, since the exhaust pipe comes to interfere with the drive shafts and the steering gear box, it is difficult to provide a compact layout.
In addition, since the exhaust pipe is constructed so as to pass behind the power unit, there is a possibility that the impact absorption effect is reduced unless the exhaust pipe easily buckles when the vehicle crashes.
The present invention has been made in view of the above circumstances, and objects thereof are to provide a compact layout for an exhaust pipe of vehicles in which an exhaust pipe extends from a rear side of a transversely mounted power unit toward the rear of a vehicle body of the vehicle, wherein the exhaust pipe is laid out in such a manner as not to interfere with drive shafts for front wheels and a steering gear box and to provide a layout for an exhaust pipe wherein an exhaust pipe is laid out in such a manner as not to interrupt the impact absorption effect when the vehicle crashes.